Warzone 2100

Warzone 2100 is a 3D real-time strategy game set on a future Earth.

Upon entering the game you land from your transport and establish your base. Here you conduct research, design and manufacture vehicles, build new structures and prepare your plans of global conquest. If the game goes badly you'll end up fighting last ditch battles here to defend your base from enemy attacks.

Combat is frenetic, with extensive graphical effects and buildings giving rise to flying shrapnel and boulders. Within the game are many different structures and vehicles. From an initial Command Center, you then go on to build Resource Extractors to provide fuel for Power Generators, which in turn supply energy to Factories, Research Facilities and weapons emplacements to protect your base.

A typical warzone game is gonna last more than a few minutes,up to a couple of hours.
And the tech tree makes up for a big part of the game's strategy. when you chhose a strategy, changing it is possible but you have to develop for it.
there are 3 preset tech levels, the highest of which has most technologies unlocked. You develop to improve them.